This invention relates to a unique and simplified method of calibrating the location of at least one laser projector relative to a workpiece.
Laser projection systems are known, and utilized to project images from a laser onto a workpiece or to digitize information about the workpiece. As examples, laser projectors are utilized to project the desired location of frame members for a truss, or the location of laminate layers for frames such as airplane fuselages. In those applications, it is important that a control for the laser projector knows where the laser is identically relative to the workpiece and a fixed reference frame. Thus, in the prior art, location sensors have been incorporated into a table or platform which holds the workpiece. In one example shown in U. S. Pat. No. 5,388,318, a series of such sensors are positioned on a table surrounding the location of the workpiece. The location of each of those fixed sensors relative to the laser projector is identified using known calibration equations; and thus a control for the system is able to calibrate the location of the laser projector relative to the table. The laser projector may then project information or images on the workpiece or table, since the laser control is able to identify the exact location of the laser projector relative to a fixed reference which supports the workpiece.
In some applications, the workpieces are simply too large to allow room around the workpieces for fixed sensors. The fixed sensor system such as disclosed in the above-referenced United States patent has proven valuable for smaller workpieces such as trusses. However, when larger workpieces are assembled utilizing these techniques, there is sometime insufficient room for several sensors to be placed around the workpiece.
In other applications, lasers may be utilized in combination with cameras to digitize information about the workpiece surface. As an example, a laser may be utilized to display the location of parts to be cut from a fabric or leather material. In such applications, the laser projector does not need to know where it is at identically relative to a fixed reference; however, the laser must be able to reference the distance between locations on the workpiece, such as flaws, etc. In other applications of digitization, the laser systems may be utilized to check the quality of the workpiece by checking the distance between features on a workpiece. As one example, a laser-based system may be utilized to check the distance between two parts on an airline fuselage.
In the prior art, the laser-based systems have typically required an extensive setup to calibrate the position of the lasers relative to fixed reference positions. This is time consuming, and requires some specific expertise in calibrating the laser or camera control relative to the position of the sensors.